Buildings-to-Grid Integration Framework

This paper puts forth a mathematical framework for Buildings-to-Grid (BtG) integration in smart cities. The framework explicitly couples power grid and building's control actions and operational decisions, and can be utilized by buildings and power grids operators to simultaneously optimize their performance. Simplified dynamics of building clusters and building-integrated power networks with algebraic equations are presented---both operating at different time-scales. A model predictive control (MPC)-based algorithm that formulates the BtG integration and accounts for the time-scale discrepancy is developed. The formulation captures dynamic and algebraic power flow constraints of power networks and is shown to be numerically advantageous. The paper analytically establishes that the BtG integration yields a reduced total system cost in comparison with decoupled designs where grid and building operators determine their controls separately. The developed framework is tested on standard power networks that include thousands of buildings modeled using industrial data. Case studies demonstrate building energy savings and significant frequency regulation, while these findings carry over in network simulations with nonlinear power flows and mismatch in building model parameters. Finally, simulations indicate that the performance does not significantly worsen when there is uncertainty in the forecasted weather and base load conditions.Comment: In Press, IEEE Transactions on Smart Gri

Heuristic optimization of clusters of heat pumps: A simulation and case study of residential frequency reserve

The technological challenges of adapting energy systems to the addition of more renewables are intricately interrelated with the ways in which markets incentivize their development and deployment. Households with own onsite distributed generation augmented by electrical and thermal storage capacities (prosumers), can adjust energy use based on the current needs of the electricity grid. Heat pumps, as an established technology for enhancing energy efficiency, are increasingly seen as having potential for shifting electricity use and contributing to Demand Response (DR). Using a model developed and validated with monitoring data of a household in a plus-energy neighborhood in southern Germany, the technical and financial viability of utilizing household heat pumps to provide power in the market for Frequency Restoration Reserve (FRR) are studied. The research aims to evaluate the flexible electrical load offered by a cluster of buildings whose heat pumps are activated depending on selected rule-based participation strategies. Given the prevailing prices for FRR in Germany, the modelled cluster was unable to reduce overall electricity costs and thus was unable to show that DR participation as a cluster with the heat pumps is financially viable. Five strategies that differed in the respective contractual requirements that would need to be agreed upon between the cluster manager and the aggregator were studied. The relatively high degree of flexibility necessary for the heat pumps to participate in FRR activations could be provided to varying extents in all strategies, but the minimum running time of the heat pumps turned out to be the primary limiting physical (and financial) factor. The frequency, price and duration of the activation calls from the FRR are also vital to compensate the increase of the heat pumps’ energy use. With respect to thermal comfort and self-sufficiency constraints, the buildings were only able to accept up to 34% of the activation calls while remaining within set comfort parameters. This, however, also depends on the characteristics of the buildings. Finally, a sensitivity analysis showed that if the FRR market changed and the energy prices were more advantageous, the proposed approaches could become financially viable. This work suggests the need for further study of the role of heat pumps in flexibility markets and research questions concerning the aggregation of local clusters of such flexible technologies.Comisión Europea 69596

Model predictive control for microgrid functionalities: review and future challenges

ABSTRACT: Renewable generation and energy storage systems are technologies which evoke the future energy paradigm. While these technologies have reached their technological maturity, the way they are integrated and operated in the future smart grids still presents several challenges. Microgrids appear as a key technology to pave the path towards the integration and optimized operation in smart grids. However, the optimization of microgrids considered as a set of subsystems introduces a high degree of complexity in the associated control problem. Model Predictive Control (MPC) is a control methodology which has been satisfactorily applied to solve complex control problems in the industry and also currently it is widely researched and adopted in the research community. This paper reviews the application of MPC to microgrids from the point of view of their main functionalities, describing the design methodology and the main current advances. Finally, challenges and future perspectives of MPC and its applications in microgrids are described and summarized.info:eu-repo/semantics/publishedVersio

Enabling solar electricity with electric vehicles in future energy systems

Tese de doutoramento, Sistemas Sustentáveis de Energia, Universidade de Lisboa, Faculdade de Ciências, 2015Climate change is on the agenda of many world leaders and policy makers, and its containment is of exceptional importance. Within this frame, ambitious environmental targets have been established by the European Union, including the reduction in greenhouse gases emissions by 80-95% until 2050. To do so, energy systems will require a large share of renewable energies, particularly solar photovoltaic power, since it appears to have the greatest potential for decarbonized electricity generation. However, relying on such renewable energy sources is expected to generate a mismatch between production and consumption, namely considerable excess solar electricity during day time. This excess power may be conveniently used to power electric mobility, taking advantage of the battery capacity of the electric vehicles acting as distributed controllable storage. In this thesis, based on 2050 scenarios for the case study of Portugal, the synergy between photovoltaics and electric vehicles is explored, determining the minimum penetration levels that allow fulfilling the climate and energy targets. It is analyzed the extent to which photovoltaic energy can further transport electrification integration, and vice-versa. The technical impacts on the electricity system are determined quantitatively, as well as the required penetration of one technology that enables the deployment of the other. Model results show that CO2 emissions targets can only be achieved with high levels of photovoltaics and electric vehicles, reinforcing the need for day time charging infrastructures, presumably at or near work facilities. It is shown that a 100% renewable energy based electricity supply is possible for certain combinations of these technologies and that the environmental targets to reduce CO2 emissions can only be reached with at least 40% of electric vehicles market share. The present thesis contributes to the literature on integration of high levels of renewable energy sources on the electric grid and on interactions between renewable energy and electric vehicles deployment.As alterações climáticas estão na agenda dos líderes mundiais e dos decisores políticos, pois contê-las é fundamental. Neste quadro, a União Europeia traçou metas ambientais exigentes, como a redução das emissões de gases com efeito de estufa em 80-95% até 2050. Para isso, os sistemas de energia terão de assentar em energias renováveis, particularmente em energia fotovoltaica, uma vez que no futuro esta parece ser a forma com maior potencial de geração de electricidade limpa. Porém, esta situação contribuirá para o desfasamento entre a produção e o consumo, com geração de energia solar em excesso durante o dia. Esta energia em excesso pode ser convenientemente canalizada para a mobilidade eléctrica, aproveitando a capacidade das baterias dos veículos eléctricos a funcionar como armazenamento controlável e distribuído. Na presente tese, com base em cenários do ano 2050 para o caso de Portugal, exploram-se as sinergias entre a energia fotovoltaica e os veículos eléctricos, determinando-se os níveis mínimos de penetração que permitem o cumprimento das metas na área do ambiente. Analisa-se em que medida a energia fotovoltaica permite uma maior integração do veículo eléctrico, e vice-versa. Os impactos na rede de energia eléctrica são determinados quantitativamente, assim como a penetração necessária de uma tecnologia que permite a implantação da outra. Os resultados do modelo mostram que as metas para as emissões de CO2 só podem ser alcançadas com elevadas penetrações de energia fotovoltaica e veículos eléctricos, o que reforça a necessidade da existência de infraestruturas para carregamento dos veículos durante o dia, tal como nos locais de trabalho. Mostra-se que 100% de energia eléctrica renovável é possível com determinadas combinações entre as duas tecnologias e que as metas ambientais para redução de emissões de CO2 são apenas alcançáveis com pelo menos 40% de penetração de veículos eléctricos no mercado. A presente tese contribui para a literatura sobre a integração na rede eléctrica de elevados níveis de energia renovável e sobre a interacção entre energia renovável e veículos eléctricos.Fundação para a Ciência e a Tecnologia (FCT), SFRH/BD/51130/201

Control of heat pumps with CO2 emission intensity forecasts

An optimized heat pump control for building heating was developed for minimizing CO2 emissions from related electrical power generation. The control is using weather and CO2 emission forecasts as input to a Model Predictive Control (MPC) - a multivariate control algorithm using a dynamic process model, constraints and a cost function to be minimized. In a simulation study the control was applied using weather and power grid conditions during a full year period in 2017-2018 for the power bidding zone DK2 (East, Denmark). Two scenarios were studied; one with a family house and one with an office building. The buildings were dimensioned on the basis of standards and building codes. The main results are measured as the CO2 emission savings relative to a classical thermostatic control. Note that this only measures the gain achieved using the MPC control, i.e. the energy flexibility, not the absolute savings. The results show that around 16% savings could have been achieved during the period in well insulated new buildings with floor heating. Further, a sensitivity analysis was carried out to evaluate the effect of various building properties, e.g. level of insulation and thermal capacity. Danish building codes from 1977 and forward was used as benchmarks for insulation levels. It was shown that both insulation and thermal mass influence the achievable flexibility savings, especially for floor heating. Buildings that comply with codes later than 1979 could provide flexibility emission savings of around 10%, while buildings that comply with earlier codes provided savings in the range of 0-5% depending on the heating system and thermal mass.Comment: 16 pages, 12 figures. Submitted to Energie

Open-Source, Open-Architecture SoftwarePlatform for Plug-InElectric Vehicle SmartCharging in California

This interdisciplinary eXtensible Building Operating System–Vehicles project focuses on controlling plug-in electric vehicle charging at residential and small commercial settings using a novel and flexible open-source, open-architecture charge communication and control platform. The platform provides smart charging functionalities and benefits to the utility, homes, and businesses.This project investigates four important areas of vehicle-grid integration research, integrating technical as well as social and behavioral dimensions: smart charging user needs assessment, advanced load control platform development and testing, smart charging impacts, benefits to the power grid, and smart charging ratepayer benefits